1. Field of the Invention
This invention relates to the testing of integrated circuit devices, and more particularly to a method and apparatus for tracking a plurality of integrated circuit devices during testing so that the test results can be correlated with the correct devices.
2. Description of the Prior Art
Testing standards for integrated circuit devices vary depending upon the application intended for the sevice. Where a lower degree of reliability is required, it is often satisfactory to provide a batch of devices with only a certain percentage of the devices meeting predetermined specifications. In these situations testing can be performed on a statistical basis, without segregating the test results for each individual device, or test results provided statistically.
Where high reliability is desired, on the other hand, it may be necessary to test each device individually and to reject all devices not meeting the required specifications. With this type of testing it is extremely important to keep track of all the devices so that the test results can be correlated with the proper devices. Any mixup can result in unacceptable devices being left in, or acceptable devices being rejected. Complicating this requirement for accurate correlation is the fact that testing is performed most efficiently when a large number of devices are tested in succession and unacceptable parts are removed only after all of the devices have been tested, rather than stopping the testing process each time an unacceptable part is encountered.
The most commonly used method for high reliability testing of integrated circuit devices, referred to as data logging, involves testing the devices in sequence and recording the test results in the same sequence, lining up the devices after testing, and loading them into container tubes. In order to properly correlate the devices in the tubes with the test results it is necesary to maintain the sequential order of both the tubes and of all devices within each tube. With this method it is possible to throw off the results of an entire test sequence by placing a single device seriously out of sequence, or by arranging the tubes in the wrong order.